Just a note about 5.1 and BBCs HDTV... for their previews, my amp reports dolby digital 5.1, but for the footy and the SD broadcasts on BBC HD1, the sound drops to pro-logic (i.e. prologic on a dolby digital stream).
For people with problems with 5.1 output via s/pdif, have you tried AC3filter?
http://www.free-codecs.com/download/AC3_Filter.htm
Still cannot receive ITV on HD - the error rate is massive and all I see on screen is a noisy frame every few minutes. Presumably ITV are broadcasting at a much smaller power level than BBC (I'm near Canary Wharf).